Research On Encoding And Decoding Of Turbo Codes And LDPC Codes

LDPC code and Turbo code all have good performance which approach to the ShannonLimit.Turbo codes are better than the other codes in low SNR.LDPC codes are relatively easy definedand can outperform the Turbo codes with sufficiently long code lengths.Its decoding complexity isalso lower than Turbo codes. Recently,Turbo codes and LDPC codes have drawn the worldwideattentions in the channel coding community due to its high performance and strong potentialapplications in practice.In part one introduces the basic theoretical knowledge,on this basis,we did a research on theencoding and decoding.we introduced the structure of the encoder and Turbo decoding algorithmwhich include MAP algorithm,improved MAP algorithm and SOVA algorithm.In order to get therelationship between its anti-interference performance and the parameters.First put the signals in theAWGN channel for transmission,the receiver use the Log-MAP decoding algorithm to obtain therelationship between BER and SNR at different parameters.Then compare the performance of MAPalgorithm,the improved MAP algorithm and SOVA algorithm at the same parameters on the sameAWGNchannel.Then change the form of the channel into Rayleigh,we obtain the performance curveof the two channel model,analysis it,provide a theoretical frame of reference for engineering.In part two,we do a analysis and research on the encoding and decoding performance of LDPCcodes.First introduced the basic principle of LDPC codes based on the information theory on thisbasis,the construction of two encoding methods,based on a random check matrix construction methodand based on a structure check matrix construction which obtain popular concern currently aredescribed.Then a further study of the coding scheme which is based on quasi-cyclic was done.Aalgorithm based on the optical orthogonal quasi-cyclic is improved.In order to get the relationshipbetween the its anti-interference performance and the parameters. First,a AWGN channel platformwas builted.Through this channel,we analyse and compare the decoding performance of differentparameters.Second,The decoding performance of the rule codes and the non-rule codes and theperformance of the different decoding algorithms was analysed and compared.Last,the performance ofthe structure proposed for the new construction method and traditional method was analyzed andcompared.